1. Technical Field
The present invention relates to a body construction, and more particularly, to an offset-crash-resistant vehicle body construction.
2. Related Arts
Vehicle bodies are divided into two major categories: bodies of construction with a frame, having a frame which is separate from the body and on which an engine, suspensions, a steering and the like are mounted; and bodies of frameless construction, having a frame integrated with the body.
A monocoque construction (unitary construction) is a frameless construction and as shown in FIG. 9 has frame parts such as a side member 2, a side sill 3, and a cross member 6 which are formed into one piece with a body 1. Generally, a body of monocoque construction is higher in rigidity and productivity and lighter in weight than a body of construction with a separate frame. Consequently, at the present time, the monocoque construction is employed in almost all passenger cars.
The aforementioned body 1 has a front body 1F which has left and right front side members 2 thereof respectively constituting lower left and right portions of the front body. Each front side member 2 has a rear end portion 2a thereof extending backward in the longitudinal direction, outward in the width direction, and downward in the height direction of the body 1 from a rear portion of an engine compartment room defined in the front body. The left and right front side members 2 are connected at their rear ends to the front ends of the left and right side sills 3, respectively. A junction between these elements 2 and 3 is indicated by reference numeral 3A. Left and right front pillars 1A extend from the front end portions of the left and right side sills 3 integrally therewith, respectively.
As shown in FIG. 10, the left and right front side member 2 have their front ends mutually connected through a front cross member 6, and intermediate portions thereof mutually connected through a chassis cross member 7. The front cross member 6 is connected to the chassis cross member 7 through a chassis center member 8.
Although the body 1 of monocoque construction has a high rigidity, it can be deformed by an excessively large external force. For example, when a car comes into an offset crash at its front left body portion as shown by the arrow A in FIGS. 9 and 10, an impact force Fa shown by the open arrow acts on the left junction 3A and the left side sill 3 through the left front side member 2. Since the left side sill 3 is located at a lower position in the height direction and at an outside position in the width direction relative to the left front side member 2, a moment M caused by the impact force Fa is applied to the left junction 3A and the left side sill 3. The moment M acts so as to bend the left junction 3A and the front end portion of the left side sill 3 upward around the point P (as viewed in the body height direction), and acts so as to bend them clockwise around the point P as viewed in a plane. Consequently, in the vicinity of the left junction 3A, the left front side member 2 and the left side sill 3 are bent, and the left front pillar 1A is receded, so that the passenger cabin is largely deformed.
The bending phenomenon is encouraged by a torsional deformation of the side sill 3 by which the side sill is largely decreased in its cross sectional area so as to be crushed. This phenomenon is further encouraged by the increase of the moment M which is caused when the left tire 10 strikes the rear end portion 2a of the front side member.
Similarly, when the car comes into an offset crash at a front right body portion, the right front side member 2 and the right side sill 3 are bent in the vicinity of the right junction 3A, so that the right front pillar 1A is receded and the cabin is largely deformed.
Furthermore, when the car is in a head-on crash as shown by the arrow B, the resultant impact force causes the body to be deformed such that the front end portions of the left and right side sills 3 are bent outward in the body width direction and downward in the body height direction, so that the cabin is deformed.